JP2010010574A - Semiconductor device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device whose incline of the semiconductor element and position of the semiconductor element for a heat spreader are easily and inexpensively controlled and its manufacturing method. <P>SOLUTION: On a heat spreader 13, in order to an unnecessary expansion of a melted solder, a solder dam 25 for shutting a flow of a melted solder so as to surround a circumference of the semiconductor element 11 protrudes with respect to the surface of the heat spreader 13. A surrounding area 251 among the solder dam 25, which faces to a surrounding portion positioned between each corner portion of four corner portions of the rectangular semiconductor element 11, is formed in parallel to the surrounding portion so as to go along near the surrounding portion of the semiconductor 11. The corner portion area 252 among the solder dam 25, which faces to the corner portion of the semiconductor element 11, is formed apart from the corner of the semiconductor element 11, and a part of the solder (melted solder) forms a solder accumulated portion P to expand outside each corner portion of the semiconductor element 11. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a semiconductor device using a semiconductor element and a method for manufacturing the same, and more particularly to a semiconductor device using a power semiconductor element and a semiconductor device in which a heat spreader is provided under the power semiconductor element and a method for manufacturing the same.

In recent years, power electronics technology has attracted attention as an environmental countermeasure technology for CO ₂ reduction represented by hybrid vehicles and electric vehicles. Power electronics technology for electric control is required not only in automobiles but also in various fields such as mobile objects that use motor drive and auxiliary robots. In these mobile applications, it is indispensable to reduce the size and weight of the electronic module, and the power module technology is a useful technology for achieving the purpose.

  Power module technology requires a structural design that efficiently releases heat from a plurality of semiconductor chips (semiconductor elements) to be mounted in order to achieve miniaturization and weight reduction. For this reason, a heat spreader formed of a block-like metal member having a high heat dissipation property is laid directly under the semiconductor chip, and the semiconductor chip with the heat spreader is mounted on a circuit board. Further, the heat spreader and the semiconductor chip are generally metal-bonded with a solder material so as not to disturb the heat dissipation.

  Here, as a conventional method of joining the semiconductor chip and the heat spreader using solder, the solder foil is placed on a semiconductor chip positioning jig, and the solder foil is used to melt and solidify the solder foil in a reflow furnace in a hydrogen atmosphere. Joining methods and joining methods in which a semiconductor chip is scrub bonded in place while supplying a solder ribbon using an automatic machine such as a solder die bonder are used for manufacturing individual semiconductor components.

  However, in the manufacture of semiconductor devices with many custom designs, it is necessary to deal with various chip types, and a more flexible and inexpensive manufacturing method has been demanded. Therefore, the inventor has been working on the application of semiconductor chips with cream solder, which is widely used for mounting as a flexible manufacturing method, and has attempted to apply it.

  The cream solder method can provide simple and inexpensive production, but has a disadvantage that the mounting accuracy is inferior to the joining method using the above-described solder foil or solder die bonder. The cause is as follows. (i) Although cream solder is supplied by printing using a metal mask, the amount of solder varies greatly depending on the accuracy of the metal mask, the particle diameter of the cream solder, and the printing conditions during printing. In addition, (ii) the solder foil method and the automatic machine method using a solder ribbon do not require flux to be contained in the solder, whereas the cream solder method requires the solder to contain flux. There is. For this reason, the flux is vaporized and scattered when the solder is melted, and the solder itself flows or swings. As a result of the above (i) and (ii), the position and inclination of the semiconductor chip are caused, which hinders wire bonding for connecting the electrodes of the semiconductor chip and an external device such as a circuit board. There was a case where damage was done.

  In addition, the solder connection portion is an important factor in the reliability of the semiconductor device. The position of the semiconductor chip relative to the heat spreader and the thickness of the solder are important because they affect the thermal conductivity to the heat spreader. In addition, the solder thickness also plays a role in absorbing thermal stress due to the difference in the thermal expansion coefficient between the semiconductor chip and the heat spreader. Therefore, the thickness management is an important factor for ensuring a reliable life.

  Therefore, conventionally, a device for making the thickness of the solder constant has been made. For example, in the semiconductor element mounting substrate described in Patent Document 1, a support base (protrusion) for supporting the semiconductor element is provided on the substrate on which the semiconductor element is mounted to prevent the inclination of the semiconductor element. Further, in the chip mounting structure described in Patent Document 2, a spacer formed of a material having a melting point higher than that of the bump is provided at a position that does not interfere with the bump provided on the bare chip to prevent the inclination of the bare chip when the bump is melted. Yes. Furthermore, in the semiconductor device described in Patent Document 3, a dam-shaped solder resist layer that surrounds the periphery of the upper surface main electrode of the semiconductor chip and is taller than the main electrode surface is formed, and then a metal component is soldered to the main electrode. This prevents unnecessary spread of the molten solder.

JP-A-9-260429 Japanese Utility Model Publication No. 4-127649 JP 2006-278441 A

  However, when the protrusions and spacers are provided to prevent the inclination of the semiconductor element as in the techniques described in Patent Documents 1 and 2, the dimensional accuracy in the height direction of the protrusions and spacers is directly measured by the semiconductor element. Affects the slope of Therefore, extremely high processing accuracy is required for processing the protrusions and spacers. In addition, such a demand for strict processing accuracy also causes an increase in cost. Therefore, from the viewpoint of preventing the tilt of the semiconductor element simply and inexpensively, it is not a realistic response. Furthermore, with the techniques described in Patent Documents 1 and 2, even if the inclination of the semiconductor element can be prevented, the position of the semiconductor element relative to the heat spreader cannot be controlled.

  Further, according to the technique described in Patent Document 3, a solder layer having a required thickness can be formed easily and inexpensively by preventing unnecessary spread of solder. The position could not be fully controlled. As a result, the connection between the semiconductor element and the external device may be hindered, or the semiconductor element may be damaged.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor device capable of easily and inexpensively controlling the inclination of the semiconductor element and the position of the semiconductor element with respect to the heat spreader, and a method for manufacturing the same. .

  The present invention provides a semiconductor device including a heat spreader and a rectangular semiconductor element connected to the heat spreader by solder so as to surround the periphery of the semiconductor element on the heat spreader. A solder dam protruding from the surface of the heat spreader for blocking the flow of molten solder, and a side facing a side located between each of the four corners of the semiconductor element among the solder dams The semiconductor region is formed in parallel to the side of the semiconductor element so as to be along the vicinity of the side of the semiconductor element, and the corner region facing the corner of the semiconductor element is formed away from the corner of the semiconductor element. It is characterized in that solder reservoirs having the same shape are formed outside each corner.

  In the invention configured as described above, the solder dam protrudes from the surface of the heat spreader so as to surround the periphery of the semiconductor element on the heat spreader, thereby blocking the flow of the molten solder. Thereby, the unnecessary spread of the solder can be prevented and the thickness of the solder can be made constant. Moreover, in the solder dam, the side region facing the side located between each of the four corners of the semiconductor element is parallel to the side so that the side of the side is near the side of the semiconductor element. The formed corner regions facing the corners of the semiconductor element are formed away from the corners of the semiconductor element, and solder reservoirs having the same shape are formed outside the corners of the semiconductor element. For this reason, due to the surface tension of the molten solder existing in the solder reservoir, each of the four corners of the semiconductor element is pulled outward, and the self-position of the semiconductor element with respect to the heat spreader is corrected (hereinafter referred to as “due to solder”). "Self-alignment action of semiconductor elements"). Here, since the respective solder reservoirs are formed in the same shape, the semiconductor element is pulled evenly, and the self-position of the semiconductor element is corrected so as to position the semiconductor element at a desired mounting position. Moreover, the tilt of the semiconductor element is also corrected by exhibiting the self-alignment action of the semiconductor element in this way.

  Furthermore, according to the solder dam described above, since the inclination and position of the semiconductor element are corrected by the self-alignment action of the semiconductor element by solder, the shape of the solder dam may directly affect the inclination and position of the semiconductor element. Absent. That is, unlike the protrusions and spacers, strict accuracy is not required for the dimension in the height direction, and the position can be corrected together with the inclination of the semiconductor element easily and inexpensively. Therefore, according to the present invention, the inclination of the semiconductor element and the position of the semiconductor element relative to the heat spreader can be controlled easily and inexpensively.

  Here, the distance from the outer edge of the semiconductor element to the solder dam (hereinafter referred to as “side distance”) in the side region of the solder dam is set to 0 to 0.2 mm, while the semiconductor element in the corner region of the solder dam is set. It is preferable to set the distance (hereinafter referred to as “corner distance”) from the vertex to the point where the straight line extending in the diagonal direction passing through the vertex and the solder dam intersect (hereinafter referred to as “corner distance”) is 1 to 3 mm. By setting the side distance as described above, the semiconductor element can be prevented from being displaced with respect to the heat spreader.On the other hand, by setting the corner distance as described above, the self-alignment action of the semiconductor element by the solder can be achieved. It can be suitably exhibited.

  Further, from the viewpoint of preventing the inclination of the semiconductor element, it is preferable that the semiconductor element is not mounted on the peripheral edge portion of the solder defined by the later-described solder capillary length (about 2.3 mm). Therefore, the corner distance is more preferably 2 mm or more.

  Moreover, if the solder pool becomes too large, the semiconductor element misalignment preventing action due to the side region of the solder dam may not be exhibited, and the misalignment of the semiconductor element (particularly misalignment due to rotation) may occur. Will increase. For this reason, from the viewpoint of reliably preventing misalignment of the semiconductor element while exhibiting the self-alignment action of the semiconductor element by the solder, when the length of one side of the semiconductor element is L, the side region of the solder dam It is preferable that the length of L is not less than L / 2 and the remainder is a corner region.

  In order to achieve the above object, the present invention provides a preparation process for preparing a rectangular semiconductor element to be mounted on a heat spreader, and a resin material is applied on the heat spreader so as to surround the periphery of the mounting position of the semiconductor element. The dam formation process for forming solder dams, the solder printing process for printing solder inside the solder dams, the element mounting process for mounting semiconductor elements on the printed solder, and the solder dam blocking the flow of solder A soldering step of melting and solidifying the solder and soldering the semiconductor element to the heat spreader, and in the dam forming step, the side portions located between the four corners of the semiconductor element in the solder dam The side region facing the semiconductor element is formed parallel to the side of the semiconductor element so that the corner region facing the corner of the semiconductor element is a semiconductor. Each corner outer sides of the semiconductor device away from the corners of the element, as the solder reservoir having the same shape with each other are formed, are characterized by forming a solder dam.

  In the invention configured as described above, a solder dam is formed by applying a resin material so as to surround the periphery of the mounting position of the semiconductor element on the heat spreader (dam forming step). After solder is printed on the inside of the solder dam (solder printing process) and the semiconductor element is mounted on the printed solder (element mounting process), the solder melts while blocking the solder flow by the solder dam. The semiconductor element is solidified and soldered to the heat spreader (soldering process). Here, in the dam formation step, the side of the solder dam that faces the side located between the four corners of the semiconductor element is arranged along the vicinity of the side of the semiconductor element. So that the corner regions facing the corners of the semiconductor element are separated from the corners of the semiconductor element and solder reservoirs having the same shape are formed outside the corners of the semiconductor element. In addition, a solder dam is formed. For this reason, in the soldering process, the self-alignment action of the semiconductor element by the solder is exhibited, and the inclination and the position of the semiconductor element are corrected. Moreover, according to the solder dam described above, the shape of the solder dam does not directly affect the tilt and position of the semiconductor element. That is, unlike the protrusions and spacers, strict accuracy is not required for the dimension in the height direction, and the position can be corrected together with the inclination of the semiconductor element easily and inexpensively. Therefore, according to the present invention, the inclination of the semiconductor element and the position of the semiconductor element relative to the heat spreader can be controlled easily and inexpensively.

  Here, from the viewpoint of forming solder dams easily and inexpensively, a thermosetting resist is printed as a resin material on a heat spreader (resist printing process), and the thermosetting resist is heated and cured (thermosetting process). preferable.

  In the resist printing step, it is preferable to print the thermosetting resist with a line width of 20 to 100 μm using an inkjet method. According to this method, the solder dam can be easily formed at a desired position and shape. Moreover, by setting the line width of the thermosetting resist to 20 to 100 μm, the solder dam can be stably formed without waste. That is, when the line width is 20 μm or more, the thermosetting resist is stably formed without interruption, and by reducing the line width to 100 μm or less, waste of material (resist material) is eliminated and the running cost is reduced. Can be achieved.

  According to the present invention, the inclination of the semiconductor element and the position of the semiconductor element with respect to the heat spreader can be controlled easily and inexpensively.

  FIG. 1 is a diagram showing an embodiment of a semiconductor device according to the present invention. The semiconductor device 1 includes a semiconductor element 11 such as a power semiconductor chip, a heat spreader 13 that diffuses heat from the semiconductor element 11, a metal circuit board 15 that is connected to an electrode of the semiconductor element 11 and a bonding wire 21. Is provided. The heat spreader 13 is formed of a block-shaped metal member in consideration of heat dissipation.

  The semiconductor element 11 and the heat spreader 13, and the heat spreader 13 and the circuit board 15 are metal-bonded using solders 23 and 24, respectively, so as not to disturb the heat dissipation. On the heat spreader 13, a solder dam 25 for blocking the flow of the molten solder so as to surround the periphery of the semiconductor element 11 protrudes from the surface of the heat spreader 13 in order to prevent unnecessary spread of the molten solder. ing. Note that all the constituent members on the circuit board 15 are sealed with a resin 27 by a transfer molding method, a potting method, or the like.

  FIG. 2 is a partial configuration diagram showing a main part of the semiconductor element of FIG. More specifically, FIG. 2A is a plan view, and FIG. 2B is a cross-sectional view taken along the line A-A ′ of FIG. As shown in FIG. 2A, the side of the solder dam 25 facing the side located between the four corners of the rectangular (square or rectangular in plan view) semiconductor element 11. The region 251 is formed in parallel with the side portion so as to follow the vicinity of the side portion of the semiconductor element 11. Further, in the solder dam 25, a corner region 252 facing the corner of the semiconductor element 11 is formed away from the corner of the semiconductor element 11. That is, the corner region 252 is provided farther from the outer edge of the semiconductor element 11 than the side region 251. For this reason, the solder reservoir P is formed so that a part of the solder (molten solder) that joins the semiconductor element 11 and the heat spreader 13 spreads outward from each corner of the semiconductor element 11. The solder reservoirs P formed outside the corners of the semiconductor element 11 have the same shape. In this embodiment, each solder reservoir P is formed in a substantially circular shape.

  By forming the solder dam 25 in this way, the semiconductor element 11 is evenly pulled outward at each of the four corners by the surface tension of the molten solder 23 existing in the solder reservoir P, and the heat spreader The self-position of the semiconductor element 11 with respect to 13 is corrected. Furthermore, the inclination of the semiconductor element 11 is also corrected by the self-alignment action of the semiconductor element 11 by such solder.

  In this embodiment, a power semiconductor chip having a size of 2 to 20 mm square, for example, is used as the semiconductor element 11. And the solder dam 25 is formed with the dimension shown below with respect to such a semiconductor element 11. That is, in this embodiment, the distance (side distance) D1 from the outer edge of the semiconductor element 11 in the side region 251 to the solder dam 25 is set to 0 to 0.2 mm, while the semiconductor element 11 in the corner region 252 is set. The distance (corner distance) D2 to the point where the straight line S extending in the diagonal direction passing through the apex and the solder dam 25 intersects from the apex is set to 1 to 3 mm. By setting the side distance D1 as described above, it is possible to prevent the positional deviation of the semiconductor element 11 with respect to the heat spreader 13, while by setting the corner distance D2 as described above, the solder 23 The self-alignment effect of the semiconductor element 11 can be suitably exhibited.

  FIG. 3 shows the relationship between the corner distance and the inclination of the semiconductor element. More specifically, FIG. 3 shows an experimental result of measuring the inclination of the semiconductor element 11 when the corner distance D2 is changed to 0, 1, 2, 3 (mm). FIG. 4 is a diagram for explaining the inclination of the semiconductor element. As is clear from FIG. 4, the inclination of the semiconductor element 11 represents the angle of the solder joint surface (lower surface) of the semiconductor element 11 with respect to the surface (upper surface) of the heat spreader 13. Here, in FIG. 4, in order to explain the inclination of the semiconductor element 11, the inclination degree is exaggerated in comparison with the actual one. The side distance D1 is set to a constant value as 0.2 (mm).

  As can be seen from FIG. 3, by setting the corner distance D <b> 2 to 1 to 3 (mm), the inclination of the semiconductor element 11 is suppressed as compared with the case where the solder pool portion P is not provided. More specifically, by setting the corner distance D2 to 1 to 3 (mm), the inclination of the semiconductor element 11 can be kept within the range of the upper limit standard value (1.0 deg.). In particular, it can be seen that the inclination of the semiconductor element 11 is suppressed within 0.4 (mm) by setting the corner distance to 2 (mm) or more. The fact that the inclination of the semiconductor element 11 is suppressed by setting the corner distance to 2 (mm) or more is supported by the following consideration regarding the capillary length of the solder.

  FIG. 5 is a view for explaining the capillary length of the solder. The capillary length is defined as follows. That is, when the droplet (solder droplet) becomes large, the influence of gravity is more dominant than the surface tension at the central portion of the droplet, so the surface of the droplet becomes horizontal. At this time, the peripheral distance (the distance from the outer edge of the drop in the horizontal direction to the area flattened by gravity in the horizontal direction) where the influence of the surface tension appears at the peripheral edge of the drop is defined as the capillary length. Here, the capillary length κ of the solder is calculated as follows. Here, λ is the surface tension, ρ is the density, and g is the gravitational acceleration.

Substituting the solder surface tension λ = 0.45 (N / m), the solder density ρ = 8890 (kg / m ³ ), and the gravitational acceleration g = 9.8 (m / s ² ) into the above formula (1). Then, when the capillary length κ of the solder is obtained, it is about 2.3 mm. Therefore, by setting the corner distance D2 to 2 mm or more, the semiconductor element 11 can be mounted in a region where the solder is flattened. Thereby, the inclination of the semiconductor element 11 can be reliably prevented while exhibiting the self-alignment action of the semiconductor element 11 by the solder.

  Note that if the solder pool portion P becomes too large, the semiconductor element 11 is not properly prevented from being displaced by the side region 251 of the solder dam 25. As a result, there is an increased risk of misalignment of the semiconductor element 11 (particularly misalignment due to rotation). For this reason, from the viewpoint of reliably preventing misalignment of the semiconductor element 11 while exerting the self-alignment action of the semiconductor element 11 by solder, the side region 251 and the corner region 252 of the solder dam 25 are It is preferable to set so. That is, when the length of one side of the semiconductor element 11 is L, it is preferable that the length of the side region 251 of the solder dam is L / 2 or more and the remainder is the corner region 252.

  Next, a method for manufacturing the semiconductor device of FIG. 1 will be described with reference to FIG. First, the heat spreader 13 and the semiconductor element 11 are prepared (preparation process; step S1). And the thermosetting resist (resin material) is apply | coated on the heat spreader 13 so that the circumference | surroundings of the mounting position of the semiconductor element 11 may be surrounded (resist printing process; step S2-1).

  Here, a contact printing method such as a silk screen can be used as a method for applying the thermosetting resist. From the viewpoint of forming the solder dam 25 with high accuracy, a line width of 20 to 100 μm using an ink jet method is used. It is preferable to print a thermosetting resist. According to this method, the solder dam 25 can be easily formed at a desired position and shape. Moreover, by setting the line width of the thermosetting resist to 20 to 100 μm, the solder dam 25 can be stably formed without waste. That is, when the line width is 20 μm or more, the thermosetting resist is not interrupted and is stably formed, and even if the line width exceeds 100 μm, there is no difference in the effect of accumulating solder, so the line width is 100 μm or less. By doing so, waste of material (resist material) can be omitted, and running cost can be reduced. Further, as shown in FIG. 2, the thermosetting resist is formed such that the corner region 252 is farther from the mounting position of the semiconductor element 11 than the side region 251.

  Thereafter, the thermosetting resist is cured by heating (heating temperature: 150 ° C., heating time: 1 h) (thermosetting step; step S2-2). As a result, solder reservoirs P are formed so as to surround the periphery of the mounting position of the semiconductor element 11 and outside each corner of the semiconductor element 11 (dam formation step). Subsequently, cream solder is printed on the heat spreader 13 (solder printing; step S3). Cream solder is printed inside the solder dam 25. That is, the cream solder is printed not only on the mounting position of the semiconductor element 11 but also on the solder reservoir P formed outside each corner of the semiconductor element 11. Then, the semiconductor element 11 is mounted on the printed cream solder (element mounting step; step S4). Thereafter, the semiconductor element 11 and the heat spreader 13 are reflow soldered (heating temperature: 250 ° C., heating time: 20 s) (soldering step; step S5).

  At this time, the flow of the melted solder is blocked by the solder dam 25, so that unnecessary spread of the solder is prevented and the thickness of the solder becomes constant. In addition, since the solder reservoir portions P having the same shape are formed outside the corner portions of the semiconductor element 11, the four corner portions of the semiconductor element are caused by the surface tension of the molten solder existing in each solder reservoir portion P. Are uniformly pulled outward, so that the self-position of the semiconductor element 11 is corrected so that the semiconductor element 11 is positioned at a desired mounting position, and the inclination of the semiconductor element 11 is also corrected. The semiconductor element 11 and the heat spreader 13 are soldered together while exhibiting the self-alignment action of the semiconductor element 11 by such solder. That is, the solder is solidified. Thus, a semiconductor element with a heat spreader is completed.

  Next, the semiconductor element with a heat spreader created as described above is mounted on the circuit board 15. First, the circuit board 15 is prepared (step S11). As the circuit board 15, for example, a metal board with good thermal conductivity and based on aluminum is used. And cream solder is printed on the prepared circuit board 15 (step S12). Subsequently, a semiconductor element with a heat spreader is mounted on the printed cream solder (step S13). Usually, a plurality of semiconductor elements with heat spreaders are mounted on the circuit board 15. Thereafter, the semiconductor element with the heat spreader and the circuit board 15 are reflow soldered (heating temperature: 250 ° C., heating time: 20 s) (step S14).

  Next, the electrode of the semiconductor element 11 and the circuit board 15 are connected by the bonding wire 21 (step S15). Finally, in order to protect the constituent members on the circuit board 15, resin sealing is performed with a sealing resin 27 by a transfer molding method, a potting method, or the like (step S16). Thus, the semiconductor device 1 is completed.

  As described above, according to this embodiment, in the solder dam 25, the side region 251 is formed in parallel to the side portion along the vicinity of the side portion of the semiconductor element 11, and the corner region 252. The solder dam 25 is formed so that the solder reservoirs P having the same shape are formed outside the corners of the semiconductor element 11 and outside the corners of the semiconductor element 11. For this reason, the self-alignment effect | action of the semiconductor element 11 by solder is exhibited, and the inclination and position of the semiconductor element 11 are correct | amended. Moreover, according to the solder dam 25 described above, strict accuracy is not required for the dimension in the height direction unlike the protrusions and spacers, and the position is corrected with the inclination of the semiconductor element 11 easily and inexpensively. be able to. Therefore, the inclination of the semiconductor element 11 and the position of the semiconductor element 11 relative to the heat spreader 13 can be controlled easily and inexpensively.

  Further, preventing the inclination of the semiconductor element 11 as described above means that the solder thickness between the semiconductor element 11 and the heat spreader 13 is formed uniformly. It is known that if the solder thickness is too small, the solder is likely to crack due to thermal stress and the reliability life is shortened. On the other hand, when the solder thickness is too thick, the thermal resistance at the solder portion increases, the power resistance is lowered, and the reliability is also adversely affected. Therefore, according to the solder thickness equalization technique based on the self-alignment effect of the semiconductor element 11 using the solder described above, a simple and highly reliable semiconductor device and a method for manufacturing the same can be provided.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, each solder reservoir P is formed to be substantially circular, but the shape of the solder reservoir P is not limited to this. That is, as long as it is provided outside the respective corners of the semiconductor element 11 so as to have the same shape, an arbitrary shape such as a rectangle or a square can be adopted as the shape of the solder reservoir P. For example, as the shape of the solder pool portion P, as shown in FIG. 7, a shape (star shape) radially extending in the diagonal direction of the rectangular semiconductor element 11 is adopted outside each corner of the semiconductor element 11. Can do. According to this configuration, the corner distance D2 can be increased with a relatively small area without increasing the area of the solder reservoir P.

  Moreover, in the said embodiment, although the solder dam 25 is formed on the heat spreader 13 before printing cream solder, it is not limited to this, The solder dam 25 is formed on the heat spreader 13 after printing cream solder. Also good. In short, the solder dam 25 may be formed before the semiconductor element 11 and the heat spreader 13 are soldered.

In the above embodiment, the heat spreader 13 is mounted on the circuit board 15 after the semiconductor element 11 is mounted on the heat spreader 13 (after the completion of the semiconductor element with the heat spreader). However, the present invention is not limited to this. The heat spreader 13 may be mounted on the circuit board 15 before mounting the semiconductor element 11 on the circuit board 13. In this case, since the solder dam 25 is usually formed on the heat spreader 13 in a state where the heat spreader 13 is mounted at a plurality of positions on the circuit board 15, the silk screen method ensures the positional accuracy of the solder dam 25. It is difficult to do. However, even in this case, the solder dam 25 can be formed on each heat spreader 13 with high accuracy by forming the solder dam 25 using the ink jet method.

  The present invention is applied to a semiconductor device provided with a heat spreader under a semiconductor element and a manufacturing method thereof. In general, it is known that a component having two or more terminal electrodes (for example, a resistor chip) has a self-alignment action by pulling the solder under both electrodes, but in the semiconductor element to which the present invention is applied, it is 1 Since there are only two bottom electrodes, it was thought that self-alignment by solder could not be expected. However, according to the present invention, even when such a semiconductor element is mounted on the heat spreader, a self-alignment effect by solder is generated, and the inclination of the semiconductor element can be suppressed.

It is a figure which shows one Embodiment of the semiconductor device concerning this invention. FIG. 2 is a partial configuration diagram illustrating a main part of the semiconductor element of FIG. 1. It is a figure which shows the relationship between corner part distance and the inclination of a semiconductor element. It is a figure for demonstrating the inclination of a semiconductor element. It is a figure for demonstrating the capillary length of a solder. 2 is a flowchart showing a method for manufacturing the semiconductor element of FIG. 1. It is a figure which shows the modification of the shape of a solder dam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor device 11 ... Semiconductor element 13 ... Heat spreader 15 ... Circuit board 23, 24 ... Solder 25 ... Solder dam 251 ... Side part region 252 ... Corner part region D1 ... Side part distance D2 ... Corner part distance P ... Solder pool part

Claims (7)

In a semiconductor device comprising a heat spreader and a rectangular semiconductor element connected to the heat spreader with solder,
On the heat spreader, further comprising a solder dam protruding from the surface of the heat spreader so as to surround the periphery of the semiconductor element and blocking the flow of molten solder,
Among the solder dams, a side region facing a side located between the four corners of the semiconductor element is parallel to the side so that the side of the side is near the side of the semiconductor element. A corner region facing the corner of the semiconductor element is formed away from the corner of the semiconductor element;
A semiconductor device, wherein solder reservoirs having the same shape are formed outside each corner of the semiconductor element.   While the distance from the outer edge of the semiconductor element to the solder dam in the side region is 0 to 0.2 mm, a straight line extending in a diagonal direction passing through the apex outward from the apex of the semiconductor element in the corner region 2. The semiconductor device according to claim 1, wherein a distance to a point where the solder dam intersects is 1 to 3 mm.   3. The semiconductor device according to claim 2, wherein a distance from a vertex of the semiconductor element in the corner region to a point where a solder dam intersects a straight line extending in a diagonal direction passing through the vertex is 3 mm or more. When the length of one side of the semiconductor element is L,
4. The semiconductor device according to claim 1, wherein a length of the side region is set to L / 2 or more, and a remainder is set to the corner region. A preparation step of preparing a rectangular semiconductor element to be mounted on a heat spreader;
On the heat spreader, a dam forming step of forming a solder dam by applying a resin material so as to surround the periphery of the mounting position of the semiconductor element;
A solder printing process for printing solder inside the solder dam;
An element mounting step of mounting the semiconductor element on the printed solder;
A soldering step of melting the solder while solidifying the flow of solder by the solder dam and solidifying the semiconductor element to the heat spreader,
In the dam formation step, the solder dam has a side region facing a side located between the four corners of the semiconductor element along the vicinity of the side of the semiconductor element. A corner region facing the corner of the semiconductor element is formed in parallel to the side, and a solder reservoir portion having the same shape is formed outside the corner of the semiconductor element and away from the corner of the semiconductor element. A method of manufacturing a semiconductor device, wherein the solder dam is formed so as to be formed. The dam formation process includes
A resist printing step of printing a thermosetting resist on the heat spreader as the resin material;
6. The method of manufacturing a semiconductor device according to claim 5, further comprising a thermosetting step of heating and curing the thermosetting resist.   The method of manufacturing a semiconductor device according to claim 6, wherein, in the resist printing step, the thermosetting resist is printed with a line width of 20 to 100 μm using an inkjet method.

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